Engines combust an air mixture and fuel within cylinders to generate drive torque. In some engines, exhaust gas resulting from the combustion is recirculated and combined with fresh air and to create the air mixture for combustion. This process is known as exhaust gas recirculation (EGR). In one implementation, the exhaust gas is recirculated from an exhaust manifold through an external EGR pipe regulated by an EGR valve and into an induction system. One benefit of EGR is a lower oxygen concentration in the air mixture, which causes decreased combustion temperatures and the generation of less nitrogen oxides (NOx).
In some engine systems, an intake oxygen sensor is implemented in the induction system to measure the oxygen concentration in the air mixture. Measurements of the intake oxygen sensor could be utilized as feedback for controlling the EGR valve. Because of a low pressure drop across the EGR valve, current diagnostic systems may not accurately detect malfunctions of the intake oxygen sensors. Therefore, while these intake oxygen sensor diagnostic systems work for their intended purpose, there remains a need for improvement in the relevant art.